Harry Kane suffered a knock to his knee in Tottenham's defeat to Gent
The striker has scored 16 goals for Spurs this season but missed 10 games at the start of the campaign with an injury.
And Allen hopes Pochettino keeps the England international out of Sunday’s game if there is any risk to his fitness.
“(Kane) had a very quiet game last night,” Allen told talkSPORT.
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They can’t afford to lose him again for a period of time
Allen on Kane
“He took a knock to the knee.
“Pochettino may just say he needs a break, if he’s not 100 per cent fit.
“Harry was disappointing in his performance last night but he wasn’t the only one. He was a bit flat.
“But they can’t afford to lose him again for a period of time.”
Kane endured a frustrating evening for Spurs in Belgium
Clive Allen wants Spurs to rest Kane
Spurs sit third in the Premier League, 10 points off leaders Chelsea.
They travel to Fulham on Sunday seeking to reattach the quarter-finals of the FA Cup for the first time since 2012.
On the game last night, Allen added: “Really disappointing performance in terms of how we know Tottenham can play. It was a strong side.
“The intention was to try to get the job done last night.
“Give Gent a lot of credit they came out and frustrated Spurs.
“It was a fair result in the 1-0 victory for them.”